Process of concentrating diluted nitric acid.



' To'ctll whom it may concern.-

UNITED sures, PAKIEN'T omen OTTO BAI'THER, OF GRIESHEIM, GERMANY, ASSIG'NOR T CHEMlSCHE FABRIK GRIESHEIM ELECTRON, OF FRANKFURT ON MAIN."

GERMANY.

nasiaaea Be it known that I, OTTO BAITHER, a subect of the German Emperor, and a resident of Griesheim-on-the-Mam, Germany, have in'-" vented certain new and useful Improvements in Concentrating Diluted Nitric Acid,' of which'the following is a specification.

As is well known, in many chemical operations, such as nitrations, &c., a diluted nitric acid is obtainedwhich in itself is of no use and can be utilized only after it has been concentrated. The method hitherto employed for concentrating the diluted nitric acid consists 1n first mixing this liquid with con-centrated sulfuric acid, then distilling this mixtulte, so that a strong nitric acidis drawn out and a diluted sulfuric acid is left behind, next concentrating this diluted sulfuric acid in' the known apparatuses used for the concentration of the sulfuric acid and afterward re mixing the concentrated sulfuric acid so ob,- tained with fresh-diluted nitric acid. This method, however, presents the following heavy disadvantages: The concentration of the nitric acid is effected in several distinct operations and requires twosets of ap aratus vi z., one for the concentration 0? the nitric acid and another for the concentration of the sulfuric acid. Moreover, it is tobe noted that by the concentration of the sul-' furic acid a most diluted sulfuric acid as a,

waste is inva'riabl obtained, which can be utilized only in t e manner that itis employed insome sulfuric-acid works as water to be added.

It will be seen that the described method of concentrating diluted nitric acid will prove economical only inicombination with a sul-v This means that the con-v furic-ac-id Works v centration of the diluted nitric acid is cons fined to certain places and that it remains so very expensive as to render the method useless in case the nitric acid is strongly diluted.-

My invention relates to a new, exceedingly cheap, and easy method of turning nitric acid diluted to any degree into concentrated nitric acid in a single operation and by means of a single apparatus.

The 'new method essentially consists in mixing the diluted nitric acid with a polysulfatein a stillat a temperature of from 110 to 130 centigrade, so that concentrated nitric acid is extracted and a hydrate ofthe poly- Specification of Letters Patent. Application filed May 22,1905. I Serial N0. 201.650. l

PROCESS OF CONCENTRATING D ILUTED NITRIC ACl Dl Batentetl Ma.y'1,. 1906 tric acid is discharged from the recipient into a convenlent storagesvessel. The hydrate of sulfate is left behind. The concentrated 111 polysulfate in the ytill is cpnstantfat the said temperature of'from 110. to L30. 'clentigrade and can be only decomposed or freed-from the water on increasing 'the te nperatur up to250 or 300 centigrade. After the water has been drawn out at this hi her-tempera ture either the ol sulfate is a lowed to cool down or it is 000 e .to a lower temperature by blowing air or the likethrough it, whereupon a freshcharge of diluted nitric acid is introduced and the whole operation is repeated, 1 The same quantity of polysulfate me be used over and over again in the still, whi e its temperature is periodically changed 'froni 110 or 130 centigrade to 250 011300 contigrade, and vice. versa.' The polysulfate" may be, for instance, acid sulfate of sodium1 that is, H Na(SO 1 g Trials have shown that the proportion ofthe quantities of the nitric acid, the water;

and the polysulfat may be varied within" certain limits; but the method will prove most economical if on every molecule of the polysulfate (H Na(SO )halfa molecule of water is taken. Then the reaction, .which is the basis of this method, is expressed by the following two equations, (:0 being the number of molecular weights of the nitric acid and 3 that of thew ater.)

2'. amtnaso tenzo):

" When, for example, a diluted-nitric acid of 40 'Baum is toz'be concentrated upto 18 thirteenhundred kilograms of the polysul:

'Baum, then into a still containingsay,

fate at 1 10 to 130 centigrade a quantity. of n from the recipient into some convenient stor- I age vessel. gThereu'pon the temperature in the'still is increased ,whenat the beginning the missing twenty per centljof the nitric acid will pass over in a state of 40 Bauin on the 5 .average and this. quantity is put back for the next following operation- After the temperature has reached 250 to 300 centigrade the remaining water w ll pass over and this water extracted'is allowed to run off. The to polysulfate left behind is allowed to cool down to its initial temperature of from110 to 130 centigrade and then again utilized for concentrating a fresh quantity of diluted nitric 1 I 5 v The distillation of the nitric acid may be considerably accelerated and at a considerably lower temperature than that mentioned above by blowing air through the mixture during the whole period of the operation, and the output of concentrated nitric acid will also be more favorable. After the extraction of the nitric acid the air blown through will also free the polysulfate from the water quicker, and, moreover, the air blown through will accelerate the cooling of the polysulfate so freed fromthe water.

-The same advantages as by the blowing through of air may be obtained by rarefying the air within the distilling apparatus during 3:) the whole operation.

It will be seen that the division of the nitric acid'and the water is not effected quantitatively. However, as any quantity of diluted nitric acid may be divided and this division 5 can be obtained in a single operation and with the same apparatus at any place, while one and the same quantity of polysulfate is used over and over' again and there are no by-products or wastes whatever, the new '40 method is far superior to the hitherto known method and it presents many important ad vantages, so that it is of great commercial value. r

- It is true that in the German Patent No.

5 106,962 a process has been disclosed in which also a polysulfate is used for the manufacture of concentrated nitric acid but there is an impbrtai'itdifference between this process andthat described-above in that the process 3, acccordin to the said German patent is not intended or the concentration of already-exi'sting diluted nitric acid, but solely for the manufacture of the nitric acid direct from saltpeter. Obviously this manufacture of the nitric acid is quite distinct from the concentration of diluted nitric acid. Also the materials used in both processes are differout, since in the method according to thesaid German patent polysulfate, sulfuric acid, and

6c Chili saltpeter are used, while in my present method polysulfate and diluted nitric acid are employed. The final products are equally different, concentrated nitric acid and water beingobtainedin the former process and 6 5 nitric acid and acid sulfate of sodium in the jcentigrade, and vice versa.

dilute latter process. For the former-process a spe- 01 al advantage 1S claimed, in that the temperature does not vary, whereas in my process the temperature 'is periodically changed from 110 or 130 centigrade to 250 or 300 Not only is my method distinct from the method described in the said German atent, but also it could not be expected at a 1 that the division of the nitric acid and the water by the hydration of the polysulfate might be extended. to such a degree that the concentration of the diluted nitric acid could be effected in an economical and profitable manner, as my trials have proved. 1

What I claim as my invention, and desire to secure by Letters Patent, is A 1. The method of concentrating diluted nitric acid, which consists in mixing the diluted nitric acid with a quantity of polysulfate in a still at from 1 10 to 130' centigrade, distilling concentrated nitric acid from the mixture at this temperature, discharging the concentrated nitric acid into a storage vessel, increasing the temperature in the still up to from 250 to 300 centigrade, so that the remaining water passes over, allowing the'latter. to run off, cooling the polysulfate in the still down to its initial temperature, and re-' peatin the operation with a fresh charge of dilute nitric acid.

- 2. The nfethod of concentrating diluted nitric acid, which consists in mixing the diluted nitric acid with a quantity of-polysulfate (H Ta(SO in a still at from 110 to 130 centigrade, distilling concentrated nitric acid from the mixture at this tempera-. ture, discharging the concentrated nitric acid into a storage vessel, increasing the temperature of the mass in the still up to from 250 to 300 centigrade, so that first the remainin nitric acid passes over in a diluted state and afterward the remaining water, uttin back the extracted diluted nitric aci for t e following operation and allowing the extracted. water to run off, coolin the .polysulfate (n nnsoga in the still down to its initial temperature, and repeatin the operatlon with a fresh charge of dilute nitric acid.

3. The method of concentrating diluted nitric acid which consists in cooling a uantlty of hot olysulfate in a still, mixing a c arge'pf d nitric acid with this polysulfate, distilling concentrated nitric acid from the nnx- I ture at thesame temperature, discharging the concentrated nitric acid into a storage vessel, increasing the temperature of the mass in the still u to such a point, that the remaining wate passes over, allowlng the latter to run off, cooling the polysulfate 1n the I25 still down to its initial temperature, and reeatin the operation with a fresh charge of ilute nitric acid.

4. The method of concentrating diluted nitric acid, which consists in constantlyblowt 1' 3o creasing the temperature of the mass in the still up to such a point, that the remaining water passes over, allowing the latter to run off, cooling the polysulfate in the still down to its initial temperature with the aid of the air blown through,;and repeatin the operation with a fresh charge of dilute nitric acid.

5. I The method of concentrating diluted nitric acid, which consists in constantly blowing air through a quantity of hot polysulfate (H NMSOQQ in a still, mixing a char e of diluted nitric acid with this polysu fate distilling concentrated nitric acid from the mixture at the same temperathe aid of the air blown throu ture, discharging the concentrated. nitric acid into a storagevessel, increasing the temperature of the mass in the still up to such a point, that first the remaining mtric acid passes over in a diluted state and afterward there inaining water, putting back the extracted diluted nitric acid for the following *operation and allowing the extracted water to rum ofi, cooling the polysulfate (H Na(SO in the still down to its initial tern erature with and repeating the operation with a fres charge of diluted-nitric acid. 7 In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses. OTTO BAITHER Witnesses:

" FRANZ HA'SSLACHER,

ERWIN DEPPEL. 

